Secondary Containment Pit

[fel3]

I'm working on a secondary containment pit for some chemical storage tanks. Originally the pit was going to be 32'x30'x5' deep and I was going to do the floor slab as one piece. However, the tank diameters have grown and now I am looking at a slab that is 49'x45'. Site soils are good (k=200 lb/ci). My analysis of the slab (using IES Visual Foundation) resulted in a thickness of 15" and #6@12" EW/EF. Opinions, please, about whether or not this slab should be done as one piece or done as four 24.5'x22.5' pieces.

Also, what about sloping the floor for drainage? On small secondary containments (say 10'x15'1.5' deep) at a 24/7 site, I have kept the floor flat (OK with the owners and obviously easier for construction). This new pit is at a remote site. There will also be some pumps and valves in the pit that will be accessed periodically and, although we are in a semi-arid region, we can get mosquitoes in the spring. The owner has gone back on forth on the issue of sloping the floor to a small sump at the center of a long wall (water will be tested before draining: clean water get pumped over the sides, dirty water gets hauled away for proper disposal). Opinions, please, on keeping the floor flat and dealing with nuisance puddling or sloping the floor (2% = about 14" of fall and 1% = half that) and dealing with variable height walls.

Thanks in advance.


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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[bridgebuster]

Placing a 49 x 45 slab in one day is possible, and easier I think. Some years ago I was resident engineer on a project where we capped 8 - 35' diameter circular bridge fenders in two days. The caps were 5' thick, sloped to drain.

Do you need to consider mass placement due to the thickness? We didn't have to, thank goodness.

Can you install sumps at each corner?